JP2010226843A - Single-phase to n-phase converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-phase to n-phase converter which is easily connected to an n-phase system ((n) is integer of 3 or above) by using n pieces of single-phase generators. <P>SOLUTION: The single-phase to three-phase converter 12 is provided with three single-phase generators 16a to 16c and a transformer 18 of three systems, whose three single-phase outputs of the single-phase generators 16a to 16c are connected to a secondary side and which outputs them into three-phase 3-wire 200 V system 36 output and supplies them to a primary side. Thus, connection to the n-phase system ((n) is integer of 3 or above) is easy by using n (n≥3) single-phase generators. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a single-phase to n-phase conversion device that interconnects (also referred to as a connection) n n-phase outputs of a single-phase generator to an n-phase system (n is an integer of 3 or more).

  For example, it would be convenient if it could be converted into a public (industrial) n-phase system, for example, a three-phase AC power source, using a single-phase generator combining a solar cell module and an inverter used for homes.

  Conventionally, when converting from a three-phase AC power source to a two-system single-phase AC power source, for example, a Scott transformer is used. Even if you consider using this Scott transformer as a transformer that converts single-phase to three-phase, the current on the three-phase side will not be balanced unless the loads on the single-phase side of the two systems (single-phase generator) are exactly the same. .

  A Steinmetz circuit is known as a circuit for converting a three-phase AC power source into a single-phase AC power source. Considering the use of this Steinmetz circuit as a single-phase to three-phase conversion circuit, it has no voltage adjustment function and is not suitable for grid connection.

  Furthermore, Patent Document 1 discloses a three-phase-single-phase conversion circuit configured to replace a Steinmetz circuit resistor with a primary winding of a transformer and connect a single-phase load to the secondary winding side of the transformer. Proposed. Even considering using this three-phase to single-phase conversion circuit as a single-phase to three-phase conversion circuit, it is necessary to adjust the capacitor and inductor according to the capacity of the single-phase generator. It is not suitable for power generators that use natural energy such as solar energy whose power generation changes every moment.

JP 2003-219646 A

  The present invention has been made in consideration of the above-described problems, and is a single-phase-n-phase that can be easily connected to an n (n is an integer of 3 or more) phase system using n single-phase generators. An object is to provide a conversion device.

  In this section, for ease of understanding, reference numerals in the attached drawings are used for explanation. Therefore, the contents described in this section should not be construed as being limited to those having the reference numerals.

  The single phase-n phase conversion device according to the present invention includes the following features (1) to (9).

(1) n (n is an integer greater than or equal to 3) single-phase generators and n single-phase outputs of the single-phase generators are connected to the secondary side and converted into n-phase system outputs for primary And n transformers to be supplied to the side.

  According to the present invention, since the n single-phase outputs of the single-phase generator are converted to the n-phase system output and provided with the n-system transformer supplied to the primary side, the single-phase generator is It is easy to connect to n (n is an integer of 3 or more) phase system.

  In the invention having the above feature (1), the n-system transformer may be configured as (2) one transformer having a separated n-phase core, and (3) each phase of the n-phase. You may comprise so that it may have.

(4) In the invention having the above feature (1), the delay power factor due to the transformer can be improved by further inserting a phase advance capacitor on the n-phase system output side of the n-system transformer. it can.

(5) In the invention having the above feature (1), power is not used on the n-phase system side by further inserting a standby power cut device on the n-phase system output side of the n-system transformer. Loss of the transformer at times can be reduced.

(6) In the invention having the above feature (4), the effect of the above features (4) and (5) can be obtained simultaneously by inserting a standby power cut device on the output side of the phase advance capacitor. Can be achieved.

(7) In the invention having any one of the above characteristics (1) to (6), by providing a coil on the n-phase system output side of the n-system transformer with a primary-side voltage adjustment tap. A desired voltage can be obtained on the n-phase system side.

(8) In the invention having any one of the above characteristics (1) to (7), a single-phase to three-phase conversion device with a simple configuration can be obtained by setting the n phase to three phases.

(9) In the invention having any one of the above characteristics (1) to (8), each of the single-phase power generators includes a solar cell and an inverter to which a DC output of the solar cell is supplied. For example, even if a single-phase power generator used for homes or the like is used, it can be easily linked to an n-phase system such as a high-power public use.

  According to this invention, it is easy to connect to an n (n is an integer of 3 or more) phase system using a single-phase generator.

1 is a configuration block diagram of a power conversion system in which a single-phase to three-phase conversion device according to an embodiment of the present invention is incorporated. It is a circuit diagram of an example of said power conversion system. It is explanatory drawing of three transformers which have a core for each phase of three phases. It is explanatory drawing of one trans | transformer which incorporates the three cores isolate | separated by each three-phase phase. It is explanatory drawing of the transformer which provided the tap for voltage adjustment in the three-phase three-wire 200V system | strain which is a primary side. It is a lineblock diagram of a power conversion system used for explanation of a phase advance capacitor. FIG. 7A is an explanatory diagram of the delay power factor with respect to the voltage of the current, and FIG. 7B is an explanatory diagram of the power factor improved by the phase advance capacitor.

  Hereinafter, an embodiment of a single-phase-n (n is an integer of 3 or more) phase converter according to the present invention will be described with reference to the drawings. Hereinafter, for convenience of understanding, the n phase is described as three phases.

  FIG. 1 is a configuration block diagram of a power conversion system 10 in which a single-phase to three-phase conversion device 12 according to this embodiment is incorporated. Here, the single-phase to three-phase converter 12 includes three single-phase power generators 16a to 16c that output a single-phase three-wire 200V system, and three single-phase three-wire 200V systems and three-phase three-wire 200V. It is composed of a single-phase to three-phase transformer 18 to be converted into a system, a phase advance capacitor 20, and a standby power cut device 22. The phase advance capacitor 20 and the standby power cut device 22 may be configured to be inserted and arranged as necessary in consideration of cost, power supply quality, and the like.

  The power conversion system 10 includes a single-phase / three-phase conversion device 12 having the above-described configuration, an industrial (public) three-phase power supply 15 of the single-phase / three-phase conversion device 12 and / or a three-phase three-wire 200V system. And a load (three-phase load) 14 to which power is supplied from.

  FIG. 2 is a circuit diagram of an example of the power conversion system 10. In the circuit diagram of FIG. 2, the phase advance capacitor 20 (details will be described later) and the standby power cut device 22 (details will be described later) in FIG. 1 are omitted.

  As can be seen from FIG. 2, the single-phase power generators 16 a to 16 c are configured by solar cells 30 a to 30 c and single-phase inverters 32 a to 32 c, respectively. DC outputs appearing between the positive side P and the negative side N of the solar cells 30a to 30c are converted into single-phase three-wire 200V systems 34a to 34c by single-phase inverters 32a to 32c, respectively, and three wires 24 (U− 0-W) to the secondary side coils of the transformers 18r to 18t.

  The single-phase three-wire 200V systems 34a to 34c are converted into three-phase three-wire 200V systems 36 by transformers 18r, 18s, and 18t, respectively, and appear in primary coils of the transformers 18r, 18s, and 18t, respectively.

  The single-phase three-wire 200V systems 34a to 34c generate an AC voltage of 100V between the U phase and the W phase with respect to the 0 phase at the outputs of the single phase inverters 32a to 32c, respectively.

  The three-phase three-wire 200V system 36 generates 200V AC voltages (phase voltages) Vrs, Vst, and Vtr on the primary sides of the transformers 18r, 18s, and 18t, respectively. The S phase is grounded in advance on the system side. The ground E of the single-phase inverters 32a to 32c is not grounded with respect to the system side, and the center tap of the secondary coil of the transformer 18 may be in a floating state. As a result, the center tap 0V of the secondary side coil of the transformer 18 is grounded.

  Loads 14 (14a, 14b, 14c) of a three-phase Δ connection (Y connection may be used) are connected to phase voltages Vrs, Vst, Vtr generated in the primary side coil of the transformer 18, respectively. In this case, line currents Ir, Is, and It flow in the R phase, the S phase, and the T phase, respectively.

  Similarly, power is supplied to the loads 14a, 14b, and 14c from the three-phase three-wire 200V system industrial three-phase power supply 15a, 15b, and 15c of each phase of the industrial three-phase power supply 15 through the three-wire 26d. The

  That is, power is supplied in parallel to the loads 14a, 14b, and 14c from the system of the single-phase / three-phase converter 12 and the system of the industrial three-phase system power supply 15 to form a system interconnection.

  As shown in FIG. 3, the transformer 18 may be composed of three transformers 18r, 18s, 18t having cores 19r, 19s, 19t for each of the three phases, as shown in FIG. Alternatively, it may be configured as one transformer 18 including three cores 19 separated in each of the three phases.

  The purpose of using the transformer 18 is first when the output side of the single-phase inverters 32a, 32b, 32c is viewed from the single-phase inverters 32a, 32b, 32c constituting the single-phase generators 16a, 16b, 16c. This is to make it appear that there are three single-phase three-wire 200V systems 34. Secondly, the primary side (industrial three-phase system power supply 15 side) and the secondary side (single-phase three-wire 200V systems 34a to 34c side) are insulated to eliminate potential mismatch. In the three-phase three-wire 200V system 36, the S phase is generally grounded as shown in FIG. Third, although overlapping with the first purpose, the voltage of the single-phase three-wire 200V system 34 is made as 100V-0V-100V.

  As shown in FIG. 5, the transformer 18 has voltage adjustment taps 51 (for 200 V) and 52 (for 205 V) on the three-phase three-wire 200 V system 36 side (also simply referred to as the system side) which is the primary side. , 53 (for 210V) is preferably provided.

  From the secondary-side single-phase generators 16a to 16c side (also simply referred to as single-phase generator side) through the transformer 18, the primary-side three-phase three-wire 200V system 36 side (also simply referred to as system side). .)), The larger the impedance of the transformer 18, the higher the voltage on the single-phase generator side than the system-side voltage. At this time, the single-phase generators 16a to 16c side If the voltage becomes too high, input limitation is imposed by the system-side voltage rise protection function on the single-phase generators 16a to 16c side, and the actual output with respect to the rated output of the power conversion system 10 may be reduced.

  The voltages of the industrial three-phase system power supplies 15a, 15b, and 15c for each phase of the industrial three-phase system power supply 15 are generally higher than 200V (about 210V) in many cases. Therefore, it is preferable to provide taps 52 (for 205V), 53 (for 210V), etc. according to the industrial voltage so as to correspond to the voltage specifications on the system side linked to the single-phase generators 16a to 16c.

  The normal transformer is designed so that the voltage on the secondary side is slightly higher than the primary side in consideration of the voltage drop due to the load. The transformer 18 of the single-phase to three-phase converter 12 is Since the energy flows from the secondary side to the primary side, the winding ratio of the primary side 200V and the secondary side 198V is designed in consideration of the voltage increase of the secondary side single-phase generators 16a to 16c. is doing.

  Next, the effect of the phase advance capacitor 20 will be described with reference to FIG. The single-phase inverters 32a to 32c used in the single-phase power generators 16a to 16c are controlled so that the power factor becomes 1, and the U− of the single-phase three-wire 200V system 34 that is the secondary side of the transformer 18 is used. The phase of the 0-W interphase voltage and the phase current are aligned. However, since the transformer 18 having inductance is provided, the power factor is lowered on the primary side of the transformer 18, that is, on the three-phase three-wire 200V system 36 side.

  In order to correct this decrease in power factor, as shown in FIG. 6, three wires 26 b (see also FIG. 1) connected to the standby power cut device 22 and three wires connected to the primary side of the transformer 18. 26a (see also FIG. 1), the phase advance capacitor 20 is inserted. The phase advance capacitor 20 is a series of an inrush prevention inductor L and a phase advance capacitor C between the R phase and the S phase, between the S phase and the T phase, and between the R phase and the T phase, respectively. Inserted in the circuit.

  Regarding the power factor, there is a guideline according to the “Resource Grid Technology Requirements Guidelines for Ensuring Electricity Quality” (October 1, 2004) of the Agency for Natural Resources and Energy, and the process proceeds from the grid on the single-phase generators 16a to 16c side. The power factor needs to be 0.95 or more.

Actually, as shown in FIG. 7A, the phase of the current is delayed by the phase θd with respect to the voltage through the transformer 18. Therefore, by providing the phase advance capacitor 20, the power factor is improved and, as shown in FIG. 7B, the phase power is corrected within the range of 1 to 0.95 as the phase θa. The voltage-current phase difference is allowed up to ± 18 ° {18 ° = COS ⁻¹ (0.95) = 18 °} according to the above guidelines.

  For example, when the impedance of the inrush preventing inductance L is set to 6% of the impedance of the phase advance capacitor C at a frequency of 50 Hz, the phase current 20 [A], the delay power factor 0.7, the phase difference 45 °, the phase voltage 200 Assuming [V], phase current 20 [A], apparent power 12 [kVA], and reactive power 8.5 [kvar], when the frequency of the power supply is 50 [Hz], C = 423 [μF], L = It can be calculated as 1.4 [mH].

  Next, with reference to FIG. 1, the effect of the standby power cut device 22 will be described. The standby power cut device 22 according to this embodiment includes a switch (switch) 23 arranged on each of the three-phase three-wire 26b and the three-wire 26c, and a control of a microcomputer or the like that turns the switch 23 on / off (opens / closes). The device 25 is configured.

  Note that the power supply of the standby power cut device 22 {the power supply supplied to each coil (not shown) of the controller 25 and the switch 23} is a two-phase of the industrial three-phase system power supply 15 as shown in FIG. For example, it is taken from the S phase and the T phase.

  The standby power cut device 22 is configured so that the standby power of the transformer 18 (the loss that the power of the industrial three-phase system power supply 15 is consumed on the primary side of the transformer 18 when the single-phase power generators 16 a to 16 c are not generating power. In order to cut the electric power), the three-phase 26b on the industrial three-phase system power supply 15 side of the phase advance capacitor 20 connected to the primary side of the transformer 18 and the three-phase industrial power supply 15 are connected. It is inserted between the three wires 26c of the load. With this configuration, standby power generated by the phase advance capacitor 20 can be cut.

  In this case, the controller 25 detects the output voltage, current, power, etc. of the solar cell 30c constituting the single-phase generator 16c, and responds when these values are below or below the reference value (threshold value). The switch 23 can be opened to control the power generated on the primary side of the transformer 18 to be cut. Since the solar cells 30a to 30c are used, the controller 25 registers area information using a timer built in a calendar clock, a so-called solar timer, at sunrise, sunset time, or before and after. It can also be configured to open and close (in simple terms, open at night and close at day). The relay switch 23 opens and closes simultaneously.

  According to the above-described embodiment, the following configuration is provided, and the following advantageous effects are provided by the configuration.

1. The power conversion system 10 is characterized in that the single-phase power generators 16 a to 16 c are connected to an n (n is an integer of 3 or more) phase system via a transformer 18.

2. The transformer 18 may be separate for each phase (FIG. 3) or may be integrated (FIG. 4). The core may be separated or integrated.

3. The three-phase three-wire 200V system side (primary side) of the transformer 18 may be Δ-connected or Y-connected.

4). It is preferable to provide voltage adjustment taps 51 to 53 (FIG. 5) on the system side (primary side) of the transformer 18.

5. Each winding is independent on the single-phase generators 16a to 16c side of the transformer 18 (FIG. 2 and the like).

6). When the output format of the single-phase generators 16a to 16c is a single-phase three-wire system, each winding U-0-W (FIG. 2) on the single-phase generators 16a to 16c side of the transformer 18 has a center tap (0 [V]: FIG. 2) is provided.

7). When a center tap is provided in the windings on the single-phase generators 16a to 16c side of the transformer 18, the center tap 0 of each winding may be grounded (FIG. 2).

8). When the center tap is grounded, the taps may be connected to each other and grounded together (FIG. 2) or each may be grounded individually.

9. The single-phase power generators 16a to 16c can be added every n units (one set), with n units (n = 3 in the above embodiment) as one set.

10. When constructing a large-capacity power conversion system, a set of single-phase generators and a transformer that matches the capacity of the set of single-phase generators are connected as a subsystem, and the subsystem is expanded. It is good.

11. When constructing a large-capacity power conversion system, m sets of single-phase generators may be prepared and connected to a transformer corresponding to the capacity of the single-phase generator m sets by m: 1.

12 When the single-phase to three-phase conversion device 12 is not operated, a standby power cut device 22 having a switch 23 may be provided and disconnected by opening the switch 23. Thereby, the standby power of the transformer 18 can be cut.

13. The relay switch 23 is controlled such that the switch 23 is opened when the output voltage, current, power, etc. of the single-phase power generators 16a to 16c are viewed and below or below the reference value. When the single-phase power generators 16a to 16c are solar power generators (see FIG. 2), a timer with a built-in calendar clock may be used. It is assumed that the switch 23 is opened and closed.

14 When monitoring the power and controlling the opening / closing of the switch 23, the switch 23 may be opened when the total generated power supplied to the secondary side of the transformer 18 falls below the loss of the transformer 18.

15. As the power monitoring method, all the single-phase power generators 16 a to 16 c may be individually monitored and summed, or may be collectively monitored at the point of input to the transformer 18. The output of one single-phase generator 16a may be monitored, and the output may be multiplied by n (3 in the above embodiment).

16. When the voltage is monitored and the switch 23 is closed, the switch 23 may be closed when the input voltage of the solar cells 30a to 30c (single phase generators 16a to 16c) becomes a certain level or more.

17. When the voltage-current phase relationship between the single-phase generator 16 side and the system side of the transformer 18 changes, the power factor can be improved by using the phase advance capacitor 20.

18. Since the single-phase generator 16 side and the system side are insulated by the transformer 18, for example, even if a ground fault occurs on the single-phase generator 16 (solar cell) side, there is no problem.

19. Even if one phase of the single-phase generators 16a to 16c is broken, the current is reduced, but the operation is continued. If the unbalance at this time is desired, the zero-phase current may be detected to detect the unbalance, and the relay switch 23 may be opened.

  The present invention has been made in consideration of the above-described problems, and is a single-phase-n-phase that can be easily connected to an n (n is an integer of 3 or more) phase system using n single-phase generators. An object is to provide a conversion device.

  As described above, the single-phase to three-phase converter 12 according to the above-described embodiment has three single-phase generators 16a to 16c and three single-phase outputs of these single-phase generators 16a to 16c. Since it is configured to include three transformers 18 that are connected to the secondary side, converted into three-phase three-wire 200V system 36 output and supplied to the primary side, n (n ≧ 3) single-phase power generation It is easy to connect to an n (n is an integer of 3 or more) phase system using a vessel.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

DESCRIPTION OF SYMBOLS 10 ... Power conversion system 12 ... Single phase-three phase converter 14 ... Load (three phase load) 15 ... Industrial three-phase system power supply 16a-16c ... Single phase generator 18 ... Transformer 20 ... Phase advance capacitor 22 ... Standby power Cutting device 23 ... switch 25 ... controller

Claims (9)

n (n is an integer of 3 or more) single-phase generators;
N single-phase outputs of the single-phase generator are connected to the secondary side, converted to an n-phase system output and supplied to the primary side,
A single-phase to n-phase conversion device. In the single phase-n phase conversion device according to claim 1,
The n-system transformer is configured as a single transformer having a separated n-phase core. In the single phase-n phase conversion device according to claim 1,
The n-system transformer is configured as n transformers for n phases. In the single phase-n phase conversion device according to claim 1,
A single-phase to n-phase conversion device, wherein a phase advance capacitor is further inserted on the n-phase system output side of the n-system transformer. In the single phase-n phase conversion device according to claim 1,
A single-phase to n-phase converter, further comprising a standby power cut device inserted on the n-phase system output side of the n-system transformer. In the single phase-n phase conversion device according to claim 4,
A single-phase-n-phase converter, further comprising a standby power cut device inserted on the output side of the phase advance capacitor. In the single phase-n phase conversion device according to any one of claims 1 to 6,
A single-phase-n-phase conversion device, wherein a primary-side voltage adjustment tap is provided on a coil on the n-phase system output side of the n-system transformer. In the single phase-n phase conversion device according to any one of claims 1 to 7,
The n-phase is a three-phase device. In the single phase-n phase conversion device according to any one of claims 1 to 8,
Each of the single-phase power generators includes a solar cell and an inverter to which a direct current output of the solar cell is supplied.

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